Funds are requested for the purchase of a Philips 410 LS transmission electron microscope. At The University of Wyoming two transmission electron microscopes are currently in use in the TEM central facility in the Department of Zoology and Physiology: a 20 year-old RCA EMU-3G used primarily for teaching and a 12-year-old RCA EMU-4C used by faculty and graduate students for research. Both microscopes remain in excellent condition and under service contract, but parts for the antiquated RCA EMU-3G become increasingly difficult to replace. A new, reliable, high resolution instrument to be used solely for biomedical research is required so that the RCA EMU-4C may be converted to teaching and general student use and the RCA EMU-3G may be retired. (A separate teaching microscope has been maintained for the University of Wyoming's programs in biological sciences because of heavy student use--85 graduate students trained over the last 12 years, 13 dissertations and 12 theses.) Award of a Shared Instrumentation Grant will allow up-to-date research as well as insure continued teaching in the electron microscopy laboratory which has become the principal TEM central facility for the U.W. (A 15-year-old Philips 300 on campus in the College of Agriculture has never been generally accessible, and its future maintenance is in serious doubt. The university maintains an SEM and microprobe in a centralized facility in the Department of Geology and Geophysics.) The university has made definitive commitments to continue maintenance of the well-established electron microscope facility as a central laboratory housed with the Department of Zoology and Physiology. Technical staff and service contracts have been funded for approximately 15 years. The university recognizes the importance of providing TEM facilities to the productive NIH-supported biomedical investigators on the faculty and to others with legitimate needs. Without SIG or similar funding, the acquisition of a new state-of-the-art electron microscope is unlikely.